A) Field of the Invention
The present invention relates to a semiconductor light emitting device and its manufacture method, and more particularly to a semiconductor light emitting device having a semiconductor light emission structure formed on a transparent single crystal substrate such as sapphire and its manufacture method.
B) Description of the Related Art
Semiconductor light emitting devices for blue light emission are widely known which utilize nitride semiconductor (called GaN series (compound) semiconductor) such as GaN, GaAlN, InGaN and InAlGaN. If a light emitting diode (LED) for blue light emission is covered with a wavelength conversion layer which contains fluorescent material, white light can be radiated. White light can be used for illumination and the like.
A GaN series semiconductor layer is generally grown on a sapphire substrate which is an insulating transparent single crystal substrate. Electrodes of an LED are therefore required to be led from the surface side opposite to the sapphire substrate. Light emission occurs in an omnidirection. Output light may be picked up from the sapphire substrate side.
Recent high outputs of light emitting diodes have broadened the markets from a conventionally used display field to an illumination field such as special illumination, general illumination and automobile illumination. The die size of LEDs has become large from about 300 μm square to 1 mm and 2 mm square. As the die size becomes large, some problems have been actualized, such as light emission variations, current supply disturbances and device exothermic.
Japanese Patent Laid-open Publication No. 2002-270905 proposes to mount a plurality of light emitting devices formed on a sapphire substrate, on one sub-mount device made of a silicon substrate by using bumps. Since a plurality of light emitting devices are integrated, a high light emission amount can be obtained. The silicon substrate having a more excellent heat radiation performance than the sapphire substrate enhances heat radiation so that since a light emission efficiency can be suppressed from being lowered by exothermic, the light emission efficiency can be improved and an excellent illumination light source can be obtained.
Japanese Patent Laid-open Publication No. 2003-110148 proposes a semiconductor light emitting device having an improved heat radiation wherein semiconductor light emitting devices are formed on a sapphire substrate which is mounted on a mount substrate, and electrical connection bumps and electrically insulated bumps are inserted between the sapphire substrate and mount substrate.
Japanese Patent Publication No. 3136672 proposes the structure wherein an i-type gallium nitride series semiconductor layer doped with p-type impurities is stacked on an n-type gallium nitride series semiconductor layer, one electrode is formed on the surface of the i-type gallium nitride series semiconductor layer, the region of the i-type gallium nitride series semiconductor layer in the peripheral area of the one electrode is etched, and another electrode surrounding the one electrode is formed on the whole circumference surface including the side wall, to make uniform the current flowing between the electrodes and to output laterally escaping light by reflecting it.
Japanese Patent Publication No. 2914065 proposes to prevent a short circuit to be caused by silver paste which is used when lead electrodes of a gallium nitride series light emitting diode are connected, by forming an insulating protective film on a semiconductor layer between a pair of electrode layers.